1. Field of the Invention
The present invention relates to a microbiological gas sampler, and especially for sampling air. More particularly, the present invention relates to a microbial air sampler used in a controlled environment.
2. Background of the Related Art
A controlled environment is an area which is designed, maintained, or controlled to prevent particle and microbiological contamination of products. Controlled environments include, for example, clean rooms and clean hoods. There are different levels of cleanliness in clean rooms, generally in the range of a Class 100 room (i.e., a room having no more than 100 particles of 0.5 micron and larger, per cubic foot of air), to a Class 10,000 clean room.
Clean rooms are used for a variety of purposes, such as in the manufacture of pharmaceutical products and electronics, such as semiconductors. Often, clean rooms are used to work on extremely expensive and complex products, and it is not unusual that there be millions of dollars worth of product in a clean room at any given time. Clean rooms have to maintain a high level of cleanliness, or risk large financial losses. If a product being developed or manufactured in a clean room becomes contaminated, the entire product in the clean room must often be discarded.
Microbial air samplers are used to monitor the level of cleanliness (in terms of viable contamination) in a controlled environment. One or more samplers are positioned about the clean room to collect airborne particulates and organisms (or microorganisms) such as bacteria and fungi. Samplers that run at high flow rates permit air to enter the sampler at such high flow rates that loss of smaller particulates carrying microorganisms is normality (i.e., smaller particulates are not retained in the medium). At the same time high flow rate air samplers only sample for a short time period and relay on a short snapshot of the condition of the area. Samplers running at 28.3 LPM (liters per minute) must operate for a longer period of time than a unit running at 322 LPM. In doing this, they sample a broader spectrum of the drug fill time and present superior data as the sample time takes a larger snapshot of the operation. Samplers that run at 28.3 LPM also provide the ability to capture more smaller particulates that may be lost due to dynamic drag (or an umbrella affect) in higher flow rate units.
Air sampling systems are generally known, and an air sampling system is offered by Veltek Associates, Inc. known as SMA (Sterilizable Microbiological Atrium) Microbial Air Sampler System. One such system is shown in U.S. patent application Ser. No. 12/068,483, filed Feb. 7, 2008 and Ser. No. 12/402,738, filed Mar. 12, 2009, and the counterpart PCT published application WO2009/100184, the entire contents of which are hereby incorporated by reference. As noted in those applications, the air sampler system includes a controller connected to a vacuum pump to control the flow of air to air sampler devices located in the clean room.
A prior art air sampler device 5 is shown in FIGS. 1-2, which is offered by Veltek Associates, Inc. The air sampler device 5 includes a top plate 10 with openings 11 and a bottom plate 14. The bottom plate 14 has a circular ridge 16 on the top surface, which receives a Petri dish 12. The underside of the bottom plate 14 has a circular channel 20 (best shown in FIG. 2) which communicates with an air port 22. A metal cover plate 26 fits over the underside of the bottom plate 14, and a rubber gasket 24 is positioned between the bottom plate 14 and the cover plate 26 to provide an airtight seal. Screws are used to secure the cover plate 26 and gasket 24 to the bottom plate 14. In addition, a circular rubber gasket (not shown, but having the shape of a washer) is positioned on the top surface of the bottom plate 14 around the circular ridge 16 to create a substantially airtight seal between the bottom plate 14 and the top plate 10.
In operation, a vacuum tube is attached to the air port 22. Air is then sucked in through the openings 11 located in the top plate 10, so that the air strikes a test medium contained in the Petri dish 12. The air then exits the device 5 through holes 18 located on the ridge 16 of the bottom plate 14. The air passes into the channel 20, and exits through the air port 22. The entire device 5 is metal, except for the gasket 24, so that the device 5 can be sterilized by heat, steam, Vaporized Hydrogen Peroxide (VHP) or Ethylene Oxide (ETO). At the end of the testing period, the Petri dish 12 is removed and analyzed to determine the level of cleanliness of the clean room.
The Petri dish 12 has a diameter of about 3.5 inches. The top plate 10 has a diameter of 4.5 inches. There are twelve holes 11 positioned within about a circular area having a 3 inch diameter, and each hole 11 has a diameter of about 0.5 inches. The sides of the top plate 10 and the bottom plate 14 are smooth.